(Sports Network) - A preseason matchup between the two worst teams in the NFL from last season normally wouldn't hold much appeal, but that won't remotely be the case when the Indianapolis Colts welcome the St. Louis Rams to Lucas Oil Stadium in the 2012 exhibition opener for both outfits.

The Colts will officially usher in the Andrew Luck era in Sunday's clash of opponents that are beginning massive rebuilding efforts under new head coaches, with the heralded No. 1 overall pick of this year's draft immediately installed as the starting quarterback in the team's first outing in 15 years where Peyton Manning won't be part of the organization.

Luck, widely considered as the most pro-ready signal-caller to come into the league since Indianapolis made the course-changing decision to select Manning with the first overall choice in the 1998 draft, clearly has some incredibly large shoes to fill. In his predecessor's 13 seasons as the Colts' field general, the team reached the playoffs 11 times while capturing eight division titles, reaching a pair of Super Bowls and claiming the 2006 world championship, with Manning garnering a record four NFL Most Valuable Player awards along the way.

Manning's unavailability for the entire 2011 season due to a serious neck injury, a prime factor in the Colts' unpopular decision to release the iconic quarterback in March, caused Indianapolis to spiral to a 2-14 finish and edge out the Rams for the right to grab Luck.

The Colts plan to play Luck for all or most of the first half in Sunday's test as they break in an offense that will have several other new parts. Coby Fleener, Luck's Stanford teammate whom Indianapolis snared in the second round of April's draft, will team with third-rounder Dwayne Allen as the starting tight ends, while a rebuilt front line will feature three regulars -- center Samson Satele, right guard Mike McGlynn and right tackle Winston Justice -- brought in through free agency.

Wholesale changes are taking place on the defensive side as well with the Colts shifting to a 3-4 alignment under first-year head coach Chuck Pagano. The most notable move involves the accomplished pass-rushing duo of Dwight Freeney and Robert Mathis, both of whom are transitioning to outside linebacker after spending their entire careers as ends.

Pagano is also holding an open audition at one of the cornerback spots, with ex-Ram Justin King emerging as the early favorite over Cassius Vaughn and Terrence Johnson. King played the previous four seasons in St. Louis and started 12 games for the Rams last year.

Coming off a tumultuous two-win season of its own, St. Louis has its share of position battles going on as well after extensively reshaping its roster under head coach Jeff Fisher, the longtime Tennessee Titans sideline boss who's returning to the NFL wars after a one-year hiatus. The Rams could have as many as seven new starters on defense, with a few of the reinforcements expected to come from a draft class that's laden with both talent and uncertainty.

Raw rookie Michael Brockers, St. Louis' first-round pick, is projected to start alongside free-agent acquisition Kendall Langford at defensive tackle, while second-round cornerback Janoris Jenkins could prove to be a steal and instant starter if he can overcome maturity issues that caused his draft stock to fall. Feisty cornerback Cortland Finnegan and linebackers Jo-Lonn Dunbar, Mario Haggan and Rocky McIntosh were also added via free agency to help upgrade a unit that ranked 31st against the run a year ago.

Another notable free-agent signee was Pro Bowl center Scott Wells, though the former Packer will sit out at least a portion of the preseason while recovering from an arthroscopic knee procedure.

These teams also faced one another in Week 1 of the 2011 preseason, a 33-10 home triumph for the Rams. St. Louis also bested the Colts at the Edward Jones by a 19-17 count in 1996, the only other exhibition encounter between the clubs.